Tunable lasers can produce outputs at a variety of wavelengths, and even non-tunable lasers can typically have their operating output frequencies altered, at least over a small range. The output frequency alteration (e.g., tunability) can occur, for example, by varying the optical or electrical power provided to the laser gain medium, or by altering the temperature of the gain medium. With this tunability comes uncertainty, which is not desirable in many applications. Often times the exact operating wavelength is important, for instance, to hit a certain absorption, transmission window, or atomic transition wavelength.
Accordingly, laser wavelength meters exist that can accept a portion of a laser's output beam, and measure the wavelength of that beam with sufficient accuracy and precision to determine whether the wavelength is correct or needs adjustment. These wavelength meters may come in a variety of sizes and performance levels. It is understood that accuracy, precision, and measurement speed may be the major performance parameters. Typical commercial units for measurement of optical frequency down to the ˜100 MHz level may be substantially large, and can make up to a thousand measurements a second.